For example, a mobile station (hereinafter referred to as an automobile) such as automobile, ship and aircraft, etc. is sometimes provided with an antenna to make mobile communication, television broadcast reception, radio broadcast reception or communication for recognition of self-position (hereinafter referred to as mobile communication) with a fixed station or a satellite station. In such communications, a very low level signal is used and therefore a high gain and high directivity antenna is often employed in order to establish clear communication by eliminating noise interference. However, such a high directivity antenna provides extremely deteriorated quality of communication or, in the worst case, cease of communication, if its direction (main lobe direction: attitude of antenna) deviates even a little. Therefore, attitude control is a very important factor for such high directivity antenna to establish high quality communication.
An antenna attitude control apparatus which tracks the signal source with a high directivity antenna by the continuous lobing system has already been proposed. Such apparatus makes reality the attitude control of antenna by scanning the main lobe of antenna and detecting relative moving direction of signal source for the antenna from change of incoming signal (changes of phase and intensity).
For instance, an antenna attitude control apparatus of the step track system samples intensity (namely receiving level) of incoming signal in every step of change (for example, 1/2 of half-value angle of antenna) in attitude of the antenna and decides the next attitude of antenna for the attitude control depending on change of intensity of the incoming signal.
However, if attitude of automobile changes suddenly, tracking for signal source by the continuous lobing system becomes difficult in some cases.
In more concrete, here considered is an example that the mobile communication is carried out by mounting an antenna on automobile and tracking the signal source in the step track system. The attitude of running automobile always changes (yawing, pitching, rolling) in accordance with road and running conditions and if such change of attitude gives change of several steps momentarily (within the period shorter than the ordinary attitude renewing period) for the antenna attitude, continuity of step tracking is lost and thereby the antenna misses the signal source.
The inventors of the present invention proposed, in order to eliminate such inconvenience, the mobile station antenna attitude control apparatus (Patent Application No. 60-066128) which forecasts the behavior of automobile using many sensors and thereby corrects antenna attitude. According to this prior art, for example, in case the apparatus of this prior art is applied to the mobile communication by the step track system explained above, if an automobile quickly changes its attitude enough to give attitude change of several steps to the antenna within a moment, since the correction for cancelling such change of attitude of automobile from the forecasted behavior thereof, continuity of step tracking is maintained and accurate tracking for signal source can be realized.
As explained above, this prior art ensures excellent trackability but also has a problem that structure and control method is a little complicated.